Hi Topbanders,
I have been scrounging together material for a short vertical which will
be dedicated for top band use.
Being a small suburban block the vertical of necessity will be short
(max 65 feet - approx 1/8th wave) and the ground radials will be hardly
enough for the job. All of this adds up to a very low radiation
resistance and so losses in the mast in the form of electrical joints
must be the best that I can make them and every other post must be a
winner and if I can save 1/2 a db here and there I will.
>From a structural point of view I have been eyeing off a 20 foot length
of 2 1/2" stainless steel pipe with a wall thickness of 1/16 of an inch
as a possible contender for the bottom section. The rest of the vertical
will be made out of fairly thick walled aluminium tubing ranging in size
from 2 3/8th" OD to 1 1/2" OD diameter. I am still weighing up the pros
and cons of either a 12 foot diameter top hat with six spokes or turning
it into an inverted "L" with the wire section folded back on itself to
cancel out some of the horizontal field.
QUESTION: Is there likely to be any measurable loss in using 20 feet of
2 1/2" stainless steel pipe as part of this construction?
Please reply direct and I will summarise the answers and post them.
73
George, VK5ALS
ggstew@bigpond.net.au
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